98 Laredo randomly stalls, engine cut outs, trouble starting, won't start, etc. - JeepForum.com
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Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > ZJ Grand Cherokee Forum > 98 Laredo randomly stalls, engine cut outs, trouble starting, won't start, etc.

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Unread 09-02-2012, 09:59 PM   #1
herqulees
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1997 ZJ 
 
Join Date: Aug 2012
Location: Nashville, Tennessee
Posts: 177
98 Laredo randomly stalls, engine cut outs, trouble starting, won't start, etc.

EDIT: Figures my first post and I mess up the title. It's a 97 Laredo, not a 98.

I have tried researching this problem all over the internet including here and haven't found any fixes for this. I bought this Jeep back in March with 139k on it after it got towed in to work as an abandoned roadside vehicle (I work for a towing company) and it sat never being claimed by it's owner. Long story short the entire thing is in great condition just needed a water pump as the one in it spit out it's bearings and it drove fine. I now have put about 5000miles on it and for the past ~1000 it has had this slowly worsening problem to the point I can't trust it to drive any more.
It started with every once and awhile the engine taking a few more revolutions on the starter before it would fire (from it's usual two revolutions to 4-6) but would still run without issue, then it started getting worse to where I could hold it on the starter some times but it would never fire (and could smell fuel from the exhaust) till I turned off and removed the key then tried again and after 10+ revolutions it would start, to the point you would have to do that and it would fire then shut off anywhere from 1 to 60 seconds after, not rough running or anything it sounds just like turning the key off, now it is to the point it can randomly revert to any of these "stages", some days it will run without a problem all day long, to other days it will refuse to start all day.
But it's general routine it has come to is it will start right up when cold in the morning and run very slightly rough, to any other person it would seem to be running fine but I know it's not as smooth as it used to be, once it warms up the engine will have random "hiccups" where I'll be driving along and the engine shuts off but the transmission keeps it at 500 to 1k RPMs till a few seconds later the engine instantly fires back up and lurches the Jeep forward then runs like nothing happened (I have to do at least ~45mph for this to happen, otherwise the engine stalls and I have to put it in N and try and try and try to restart it, sometimes it will, other times I'm stuck on the side of the road for two minutes), most times I come to a stop, am driving at idle (ex. drive thru lines) it will shut off with no warning and refuse to restart for a couple minutes, the first minute or so it won't try at all to start, then it will transition to trying but failing to start and finally it will barely start and I can rev it up and it'll run from anywhere from two seconds to the rest of the day, if it dies again the entire process of restarting is, well, restarted.

Like I said when it's running it runs like a dream, but this problem always strikes at random and I have yet to find a fix. I have replaced the CPS, then replaced spark plugs, wires, distributor cap, and distributor rotor, then replaced the coil after testing and finding it bad, then rebuilt and cleaned the entire throttle body, and finally I removed and cleaned the ECM and it's connectors with electrical cleaner spray and covered it's plugs with dielectric grease, after the final repair it seemed like it fixed it, started up normally, no random hiccups or stalls, put it through thirty miles of stop go traffic and stopping at a couple stores finishing up errands before finally coming home and shutting it off for the day happy to not have any problems, then the next day (today) it starts up fine and I go to the gas station to fill it up, after done filling it I pop the hood and start it so I can check the transmission fluid and it dies as I open the hood, I cuss and restart it and before I can get out of the drivers seat it shuts off again, restart it and I make it to pulling the dip stick out and it shuts off, restart it AGAIN and finally make it through checking the transmission and closing the hood then as I get ready to leave it shuts off, I start it yet again and drive back home with no problems then drive all the way up to Kentucky because a friend needed a ride and even after warning him of my temperamental Jeep he still wanted a ride and the entire way up there (about 150miles) with stops for snacks and everything including 4WD across his muddy five acre yard to tow out his riding lawn mower before I left that stopped working LOL it gave me zero issues.

I am lost! Can anyone please help? I'm hoping it's not the ECU but it seems to be pointing towards it...

EDIT: Forgot to add, fuel pressure has been tested as fine, and the MIL has not come on once the entire time I have owned this Jeep, and no codes have ever come up after all the times I've scanned it other than a random one for the fuel gauge which tends to randomly read as Empty, seems to be a common problem with the ZJ.


Last edited by herqulees; 09-02-2012 at 10:36 PM..
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Unread 09-02-2012, 10:46 PM   #2
ZeeJay1997
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Location: Sweet Home, Alabama
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Quote:
Originally Posted by herqulees View Post
I'm hoping it's not the ECU
Sounds a lot like it. Did you wiggle the plugs while it's running?

See this post for more:

http://www.jeepforum.com/forum/f13/1...talls-1407423/
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Unread 09-02-2012, 10:51 PM   #3
Oldfrog
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1997 ZJ 
 
Join Date: Feb 2008
Location: Louisiana/Texas
Posts: 4,222
It's the PCM ( or ECU...same thing)...I'm 90% certain.
You can repair it yourself, as described in the above write up, or buy one at O'reilly's ( Cardone brand)...but do NOT buy one from either of the 2 outfits in Florida.
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Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
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Unread 09-02-2012, 10:51 PM   #4
JasonStebbins
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There's no way I'm reading that essay you just wrote.

Crank Position Sensor - MOPAR. Don't buy one at the parts store because most likely it won't work.

Throttle Position Sensor.

Failing fuel pump/clogged fuel filter.

Check battery terminals AND a few inches of the wires under them. Check the battery ground to the fender.

Clean/replace the Idle Air Control.

Wiggle the PCM while running, if there is any change in idle it needs replaced.

The fuel gauge is probably a bad sending unit. Was the culprit in mine.
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Unread 09-02-2012, 10:59 PM   #5
JS97ZJ
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1997 ZJ 
 
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It sounds like the PCM.
While the engine is running, tap on the 3 connectors that plug into the PCM. If it hicups or dies it's the PCM. You can also put ty-wraps around the PCM and the plugs and tighten it up real good. If that works for you it's once again the PCM.

Other things can cause this problem
1. crank sensor
2. TPS
3. coil (secondary wiring)

but try the tapping,ty-wrap tricks first. If the first proceedures work for you, you'll have to replace the computer or repair it yourself.


http://www.jeepforum.com/forum/f13/9...tures-1303589/
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Unread 09-02-2012, 11:12 PM   #6
herqulees
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I've tried multiple times to wiggle the plugs and it's never caused anything to happen. And the CPS I replaced it with is a Duralast with lifetime warranty. I just could not justify paying $140 for a CPS with a 90day warranty when autozone has a $45 one with lifetime. I am going to try the ziptie idea and see if it does any good. If I don't stall in Nashville traffic when I drive to/from work this week I know what it is then. And to Jason I don't blame you, my first thought was "Holy crap." after I started the thread. :P But over all... I can't really shorten it without removing how the issues progressed worse over time.
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Unread 09-02-2012, 11:17 PM   #7
JS97ZJ
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Quote:
Originally Posted by herqulees View Post
But over all... I can't really shorten it without removing how the issues progressed worse over time.
That what usually happens when the computer's connections start to worsen. Just make sure the ty-wraps are tight.
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Unread 09-02-2012, 11:28 PM   #8
Oldfrog
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Jeeps prefer the OEM CPS.....just sayin'...
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Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
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Unread 09-02-2012, 11:28 PM   #9
herqulees
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Quote:
Originally Posted by JS97ZJ View Post
That what usually happens when the computer's connections start to worsen. Just make sure the ty-wraps are tight.
We have another 1997 ZJ 4.0 on the yard that is due to go to auction, only difference is it is a Limited and 2WD instead of my Laredo 4WD.
Would I be able to temporarily swap ECMs and try that one out or is their some security or feature difference to where it won't work on my Jeep? Figure that could be a good free resource to verify if it's my ECM or not if it's possible before I go digging through junk yards.
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Unread 09-02-2012, 11:31 PM   #10
Oldfrog
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Look ...here's the deal. Like it or not, one day, if not today, your 97 WILL need a new PCM. Make no mistake about it. It's going to happen. Why not just either fix yours or swap it now and eliminate it as the cause of your troubles?
You might get lucky. Trust me, I've been there. $800 later, I swapped the PCM and everything was fine again.
__________________
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Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
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Unread 09-02-2012, 11:32 PM   #11
JasonStebbins
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1997 ZJ 
 
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Quote:
Originally Posted by herqulees View Post
And the CPS I replaced it with is a Duralast with lifetime warranty.
Problem solved. Get a Mopar CPS and watch your symptoms disappear.
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Unread 09-02-2012, 11:35 PM   #12
herqulees
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1997 ZJ 
 
Join Date: Aug 2012
Location: Nashville, Tennessee
Posts: 177
Quote:
Originally Posted by Oldfrog View Post
Jeeps prefer the OEM CPS.....just sayin'...
Well I guess if the ECM ends up passing that will be my next thing to work on replacing. Suppose at least once I return the Duralast one that will pay for... one third of the Mopar one. Lol
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Unread 09-02-2012, 11:38 PM   #13
herqulees
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1997 ZJ 
 
Join Date: Aug 2012
Location: Nashville, Tennessee
Posts: 177
Quote:
Originally Posted by Oldfrog View Post
Look ...here's the deal. Like it or not, one day, if not today, your 97 WILL need a new PCM. Make no mistake about it. It's going to happen. Why not just either fix yours or swap it now and eliminate it as the cause of your troubles?
You might get lucky. Trust me, I've been there. $800 later, I swapped the PCM and everything was fine again.
I'm not one to just throw parts at vehicles. I'd rather test and verify that it's the ECM instead of spending $140 on a CPS, then $800?? on an ECM, then idk $50 on new ECM wiring plugs, and then find out it was a loose ground somewhere or something and a five minute fix.
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Unread 09-03-2012, 12:12 AM   #14
JasonStebbins
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It's definitely the Duracrap CPS you installed.

Have you ruled out a clogged/failing catalytic converter?
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Unread 09-03-2012, 12:29 AM   #15
JS97ZJ
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I've never tried swapping out a limited with a Laredo, but you could go for it. I'd work with what you have. Do the ty-wrap thing.

Right now I'm re-flowing another PCM as we speak. It's been the 4th PCM the guy's had in his jeep, and the only thing that keeps it running is the ty-wraps.

These remans suck. These computers are coming out of used jeeps, getting painted and are being sent out as re-manufactured. It's pot luck in getting one that actually works or have been repaired. If you checked out the the repair link you'll see it's not a quick procedure. If these repair shops actually did the re-flow job on them, just the cost in time would be high.

If you get no satisfaction with the ty-wraps, then try the other suggestions. There are procedures for testing the other components that can cause this problem. I found the ty-wrap method fast and cheap.
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